Conventional stamping machines use hitch type feeds which advance the material to be stamped and/or formed through one or a series of dies mounted in a stamping press, the finished product then being collected after discharge from the stamping operation after being acted upon by the die or dies. Generally, the stamping press hits in a repetitive up-down motion, closing and opening the die in one positive movement every short fraction of the stamping press cycle, the material then, with the die open, being advanced one pitch into its next dormant position, ready to receive the next closing and opening sequence of the die by the said roll or hitch feeding machine. Some such devices have been described in a variety of patents such as (1) U.S. Pat. No. 3,180,294 (Daalderop), (2) U.S. Pat. No. 3,470,726 (Richter) and Australian Pat. No. 120,905 (Kretz).
These material feeding mechanisms fail to hold the material to be stamped accurately within the die, so that the pitch, from one stamping to the next, cannot hold a consistent specified dimension. To achieve accuracy of pitch, dies have been equipped with pilots which are expensive, difficult to maintain, slow production and reduce efficiency of operation.
The invention contemplated herein departs radically from the conventional by replacing any material feeding mechanism by utilizing the die itself, after closing and penetrating the material, to advance to the next position, carrying the material forward, thus opening and freeing the material. The die thereafter returns to its original starting position to start the next stamping operation or cycle. Hence, in place of a die being in a fixed position operated by an attachment to an up-down motion of a conventional stamping machine, the die being closed and opened without interruption in a short fraction of the cycle (stroke) of the stamping press, there is instead a die unattached to the operating stroke of the stamping press. Actually, the die is mounted on a carriage which in-line travels back and forth and carries with it the punch through the facility of punch and die assembly a measured distance for the desired pitch, and which otherwise closes at one end and opens at the other end of the carriage travel. In place of permanent attachment of die to stroke of the stamping press, an intermittent is used, operative only at each end of the carriage travel; the cycle (stroke) of the stamping press for the die to dwell in its closed position in one direction, and in its open position in the other direction, of its back and forth motion.